The invention concerns a structure between a driving transmission and a roll.
Known in the art is a bellows seal structure between a driving transmission and a variable crown roll. In this application, a variable crown roll means one where the roll jacket can be loaded along its length into the desired shape by using hydraulic pressure or hydraulic loading shoes. The central shaft at which the hydraulic counter-pressure is directed or where the hydraulic loading shoes are located, is a fixed and static shaft. To allow radial and axial motions for the roll jacket of the variable crown roll used in the connection between the driving transmission and the roll, a state-of-the-art solution allows the said motions by using a bellows-like seal structure made of rubber between the driving transmission and the roll. In the known state-of-the-art solution the bellows are fitted in between the end face of a toothed gear surrounding the shaft of the variable crown roll of the driving transmission and a body structure joined to the driven roll after the sleeve shaft of the toothed gear.
The bellows allow large radial motions between the roll structure and the transmission. The rubber bellows are joined by band clamps both with the transmission and with the body part connected to the roll jacket. The transmission oil is located inside the bellows in a space between the bellows and the static central shaft. The rubber bellows are attached by hose clamps between the roll and the toothed gear.
The bellows do not adapt so well to reception of axial motion, radial motion and torsion at high speeds and with big diameters. Should the bellows tear or the clamp break, the resulting leakage will be so big that the entire paper machine must be stopped, so the problem will also come as a surprise, and not as a controlled one.
The present application presents a seal solution of an entirely new type for the driving transmission and roll. The roll may be a variable crown roll in a paper machine, which includes a static, non-rotary central shaft and a joining hydraulically loaded pressure chamber or joining hydraulically loaded loading shoes, which are used or which bring about a pressure in the pressure chamber which is used for loading the roll jacket and for controlling in the roll nips the bending shape of the roll jacket. Through the driving transmission the drive is transferred first from the sleeve shaft through the body part to the roll flange and then to the roll jacket. Bends caused by the hydraulic pressure or by loading applied by the loading shoes are permitted on the central shaft itself. The idle bearing on the drive side of the static shaft is preferably located in connection with the driving transmission.
The sealing between the integrated roll transmission and the roll must receive
axial motion, the roll jacket may move a distance equal to clearances between bearings
radial motion, eccentricity caused by bending of the roll
torsion, a motion caused by backlashes in the gear clutch.
The new seal solution is formed by a sealing ring. The excellency of the structure is based on low friction and on a light-weight sliding ring material, which in addition includes wear-resistant seals in both the axial and radial directions. The sliding ring is located between two lateral sealing rings, whereby the place is determined axially. The sliding ring is dimensioned so that any eccentricity between central lines of the shaft introduced by the transmission and by the loading of the roll will cause no problems for its operation, as the sliding ring may move in its position in the radial direction. A small grease filling is placed in the space remaining inside the sliding ring and the rings to attend to lubrication of seals in the axial direction with the aid of centrifugal force. The seal located on the outer diameter of the sliding ring gets its lubrication from oil inside the transmission. Dimensioning of the seal surface is sufficiently long, so that an axial motion of the jacket will not prevent the operation.
All rings rotate at the rotational speed of the roll. The sliding ring gets into a constant small radial motion, the extent of which depends on the loading of the roll and on the magnitude of the estimated eccentricity. The seal solution is suitable for diameters of all sizes, it is also suitable for both low and high surface velocities. The sliding ring and the seal materials are chosen so that they will withstand well the wear in question. The sealing solution does not aim at an entirely leakage-free solution, but at controlled leakage. From the space outside the sealing a hose/pipe extends in which the leakage can be observed, and wearing of the seals can be foretold so that the suitable time for maintenance can be planned in advance.
The new solution allows sealing of new high-speed machines.